Organic polymers are usually thought of as being materials of high electrical resistance. Indeed, most modern insulation is made out of organic polymeric materials. However, relatively recently it has been discovered that organic polymers can be made which are conductive. The best known and most conductive of these polymers is polyacetylene. Other conductive polymers include polypyrrole and polyphenylene sulfide. Many of the conductive polymers are made conductive by adding dopants, such as arsenic pentafluoride, iodine bromine, sulfuric acid, alkaline metals, and other chemicals, to the monomer prior to polymerization.